1. Field of the Invention
The invention relates to thermoplastic compositions having improved properties and a process for preparing the compositions. Optionally, these blends may be dynamically vulcanized.
2. Description of Information Disclosures
In recent years, there has been a significant commercial interest in polymer blends which have a combination of both elastic and thermoplastic properties. These polymer blends have been given the generic designation of Thermoplastic Olefins ("TPO"). They exhibit some of the properties of a cured elastomer as well as the reprocessability of thermoplastic resins. The elastomeric characteristics may be enhanced if one component of the blend is a vulcanizable elastomer which is wholly or partially crosslinked.
U.S. Pat. No. 4,130,534 discloses elastoplastic compositions comprising a blend of a thermoplastic crystalline polyolefin resin and a rubber which may be butyl rubber, chlorobutyl rubber or bromobutyl rubber.
U.S. Pat. No. 4,172,859 discloses a thermoplastic composition containing a polyamide matrix resin and at least one polymer having a specified tensile modulus.
U.S. Pat. No. 4,174,358 discloses a thermoplastic composition containing a polyamide matrix resin and at least one polymer having a specified tensile modulus.
The earliest work in the curing of TPO compositions was by Gessler and Haslett; see U.S. Pat. No. 3,037,954. That patent teaches the concept of "dynamic curing" wherein a vulcanizable elastomer is dispersed into a resinous thermoplastic polymer and the elastomer cured while continuously mixing and shearing the polymer blend. The result is a micro-gel dispersion of cured rubber in an uncured matrix of resinous thermoplastic polymer. Gessler's U.S. Pat. No. 3,037,954 discloses compositions comprising polypropylene and a rubber wherein the rubber may be, butyl rubber, chlorinated butyl rubber, polybutadiene, polychloroprene and polyisobutene. Compositions of about 50 to 95 parts polypropylene and about 5 to 50 parts of rubber are disclosed.
U.S. Pat. No. 4,639,487 discloses a heat shrinkable thermoplastic composition of an ethylene copolymer resin with a dynamically vulcanized halogenated butyl rubber.
Dynamically vulcanized thermoplastic compositions comprising a polyamide and various types of elastomers are known. See, for example, U.S. Pat, No. 4,173,556; U.S. Pat. No. 4,197,379; U.S. Pat. No. 4,207,404; U.S. Pat. No. 4,297,453; U.S. Pat. No. 4,338,413; U.S. Pat. No. 4,348,502; and U.S. Pat. No. 4,419,499.
U.S. Pat. No. 4,287,324 discloses a dynamically vulcanized composition comprising a blend of a crystalline polyester and a cured epichlorohydrin.
U.S. Pat. No. 4,226,953 discloses a dynamically vulcanized composition comprising a blend of styrene-acrylonitrile resin and a nitrile rubber.
U.S. Pat. No. 4,350,794 discloses a polyamide molding and extrusion composition prepared by melt blending a polyamide resin and a polyamide reactive halogen functional elastomer.
There is still a need to improve the properties of uncured and of dynamically vulcanized alloys.
It has now been found that compositions comprising a thermoplastic engineering resin and a halogen-containing copolymer of an isoolefin and a para-alkylstyrene have improved properties, such as higher Vicat softening temperature, lower oil absorption, resistance to compression set, and retention of properties after heat aging. Moreover, these compositions may be stabilized to ultraviolet light exposure without adversely affecting their properties. The compositions may also comprise uncured or dynamically cured elastomers.